1. Technical Field
The present invention relates to a measuring apparatus.
2. Related Art
Various types of measurement that use a semiconductor laser for measuring oscillation, distance, velocity or the like of an object to be measured are known.
Such measurements use the self-coupling effect of the laser. The self-coupling effect of the laser is an effect where returned light or reflected light of a laser beam is amplified in a laser medium, and as a result, the laser oscillation state is modulated. For a semiconductor laser with high gain, even if the returned light has an intensity of less than one hundredths that of an emitted laser light beam, the state of the returned light may be observed at a high signal to noise ratio (SNR).
When the returned light is subjected to frequency shifts due to the Doppler effect, or the position of reflection from the object to be measured is varied and is subjected to phase modulation, the oscillation state of the laser due to the self-coupling effect may vary in accordance with the changes. By analyzing the variations, the velocity or displacement of the object may be measured.